In June 2012 the U.S. Food and Drug Administration (FDA) approved using the targeted therapy medicine Perjeta (chemical name: pertuzumab) in combination with Herceptin (chemical name: trastuzumab) and Taxotere (chemical name: docetaxel) to treat HER2-positive, metastatic breast cancer that hasn’t been treated with either Herceptin or chemotherapy yet. (Perjeta was called Omnitarg in earlier studies.)

Metastatic breast cancer is cancer that has spread to parts of the body away from the breast, such as the bones or liver.

The FDA approval was based on results from the CLEOPATRA (Clinical Evaluation Of Pertuzumab And TRAstuzumab) study. The study showed that women diagnosed with metastatic, HER2-positive breast cancer who were treated with a combination of Perjeta, Herceptin, and Taxotere lived 6 months longer without the cancer growing (progression-free survival) compared to women treated with only Herceptin and Taxotere.

On June 21, 2012 Genentech, the company that makes Perjeta, announced that more results from the CLEOPATRA study showed that women who got Perjeta, Herceptin, and Taxotere had better overall survival (the time a woman lives with or without the cancer growing) than women who got only Herceptin and Taxotere.

HER2-positive breast cancers have too many copies of the HER2/neu gene, which make too much of the HER2 protein. HER2-positive breast cancers tend to be more aggressive than cancers that are HER2-negative. Both Herceptin and Perjeta work against HER2-positive breast cancers by blocking the cancer cells' ability to receive growth signals. Both medicines are given intravenously.

Herceptin, also a targeted therapy medicine, is FDA-approved to treat advanced-stage, HER2-positive breast cancer and to lower the risk of recurrence (the cancer coming back) of early-stage, HER2-positive breast cancer with a high risk of recurrence.

Earlier research suggested that Perjeta could boost Herceptin’s ability to weaken or destroy HER2-positive breast cancers. So the CLEOPATRA study looked to see how the two medicines could be used together to treat HER2-positive breast cancer. Doctors sometimes call the Herceptin-Perjeta combination “dual HER2 antibody therapy.”

In the CLEOPATRA study, 808 women diagnosed with HER2-positive, metastatic breast cancer that hadn't been treated yet were randomly assigned to receive one of two treatment regimens:

half the women got Herceptin, Taxotere, and Perjeta

half the women got Herceptin, Taxotere, and a placebo infusion (instead of Perjeta)

More than 80% of women who got Herceptin, Taxotere, and Perjeta had some response to the treatment compared to 69% of women who got only Herceptin and Taxotere.

The women who got Herceptin, Taxotere, and Perjeta lived 18.5 months without the cancer growing (progression-free survival) compared to 12.4 months for the women who got only Herceptin and Taxotere -- a 6-month improvement.

Genentech hasn’t said how much overall survival improved with Perjeta, but did say the results would be presented at an upcoming meeting of cancer specialists. In December 2011, when the CLEOPATRA study results were presented at the 2011 San Antonio Breast Cancer Symposium and published in the New England Journal of Medicine, 17% of the women who got Perjeta had died compared to 24% of the women who didn't get Perjeta.

There was only a small increase in side effects in women treated with Herceptin, Taxotere, and Perjeta compared to women who got only Herceptin and Taxotere.

The most common serious side effects in both treatment groups were low white blood cell counts (called neutropenia), with or without fever, and severe diarrhea. Problems with heart function or developing heart failure can sometimes be side effects of Herceptin. The CLEOPATRA study found that adding Perjeta didn't increase the risk of heart problems.

If you're being treated for metastatic, HER2-positive breast cancer, it’s a good idea to ask your doctor about the FDA approval of Perjeta and whether Perjeta should be part of your treatment plan.